1. Field of the Invention
The present invention relates to a liquid ejecting head to be mounted in an inkjet printer or the like and a method for manufacturing the same.
2. Description of the Related Art
Injection of liquids (e.g., ink) in the course of producing a liquid ejecting head and discharging of entrained bubbles after ejection of droplets are important factors for facilitating the production of the head and stabilizing the ejection of droplets. As a method for favorably performing these factors, Japanese Patent Application Laid-Open No. H09-239992 describes a method for hydrophilizing a channel portion of an inkjet nozzle.
Recently, since the number of ejections of ink droplets per time is increased due to improvement in printing throughput of an inkjet printer, the temperature of an inkjet recording head has tended to be raised in use. Japanese Patent Application Laid-Open No. H09-239992 describes an inkjet recording head having a hydrophilized layer including a fired layer of perhydropolysilazane on an inner wall surface of a channel, wherein the hydrophilized layer is formed of an inorganic material and other wall portions of the channel are formed of an organic material. The linear expansion coefficient of the inorganic material may be different from that of the organic material by 4 times or more, and there has been a case that the temperature of the head is raised in use and the hydrophilized layer peels off. Hence, there has been a demand for forming the hydrophilized layer from a resin which is an organic material, namely, for hydrophilizing the inner wall surface of a channel with a resin.
As a method for hydrophilizing the inner wall surface of a channel with a resin, for example, a method is considered in which a nozzle layer having an ejecting port and a liquid channel is formed in a two-layer configuration and a first layer of the two layers at the side of the channel is formed into a hydrophilized layer. As a method for manufacturing an inkjet recording head having such a configuration, a method is considered in which materials for a first layer and a second layer are applied with being stacked on a mold material which is produced by patterning and with which a portion to be subsequently formed into a channel is to be filled, to thereby form the layers. In the manufacturing method, the wall surface of the ejecting port is formed in a laminated structure of the second layer and the first layer.
The hydrophilized layer in the wall of liquid channel is required to be thin and to have no variation between nozzles. In the case that the hydrophilized layer is an inorganic film, the material for each layer can be uniformly formed into a film (film-formed) on the mold material (even if there are irregularities on the mold material) by a CVD process or the like. However, in the case that the hydrophilized layer is an organic film such as a film of a resin material, the above method cannot be adopted, and the material is commonly applied by using rotation, thereby making it very difficult to control the thickness of the hydrophilized layer (first layer) in the wall of the liquid channel and coatability on the end portion of the mold material in some cases. For example, if the hydrophilized layer is made thinner, the mold material may be deteriorated for the coatability of the end portion and the inner wall surface of the channel may not be hydrophilized. On the other hand, if the film thickness is increased in order to enhance the coatability of the hydrophilized layer on the end portion of the mold material, the film thickness of the hydrophilized layer in the wall of liquid channel may be uneven in a nozzle array, thereby causing variation in ejecting characteristics among nozzles in some cases.
Accordingly, an object of the present invention is to provide a liquid ejecting head where the hydrophilized layer does not peel off in use and the filling with a liquid (e.g., ink) and removal of entrained bubbles are easy. Another object of the present invention is to provide a method for manufacturing a liquid ejecting head which has no variation in ejecting characteristics among nozzles and in which a thin and uniform hydrophilized layer can be formed.